Longitudinal members, such as spinal rods, are often used in the surgical treatment of spinal disorders such as degenerative disc disease, disc herniations, scoliosis or other curvature abnormalities, and fractures. Treatment of these spinal disorders may use different types of surgical treatments. In some cases, spinal fusion is indicated to inhibit relative motion between vertebral members. In other cases, dynamic implants are used to preserve motion between vertebral members. For either type of surgical treatment, longitudinal members may be attached to the exterior of two or more vertebral members, whether it is at a posterior, anterior, or lateral side of the vertebral members. In other embodiments, longitudinal members are attached to the vertebral members without the use of dynamic implants or spinal fusion.
Longitudinal members may provide a stable, rigid column that encourages bones to fuse after spinal-fusion surgery. Further, the longitudinal members may redirect stresses over a wider area away from a damaged or defective region. Also, rigid longitudinal members may restore the spine to its proper alignment. In some cases, flexible longitudinal members may be appropriate. Flexible longitudinal members may provide other advantages, such as increasing loading on interbody constructs, decreasing stress transfer to adjacent vertebral members while bone-graft healing takes place, and generally balancing strength with flexibility.